Enclosed variable condenser



June l2, 1951 H. c. M. I ONGACRE 2,556,846`

ENcLosEn VARIABLE coNDENsER Filed Dec. l5, 1948 `l l E 4 E 2?: d@

:i b @j E N \\Q E f *Ns 'j u 5P@ E NNE ig .n y 1 @i xi M 1 i i:

3 INVENTOR. I Hen/y MLU/(gade S u EXW-JJM HMO/'neg Patented June l2, 1951 UNITEDSTATES PATENT OFFICE ENCLOSED VARIABLE CONDENSER Henry C. M. Longacre, Floral Park, N. Y., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application December 15, 1948, Serial No. 65,470

2 Claims. (Cl. F75-41.5)

This invention relates to variable electrical condensers.

Electrical condensers have been hermetically sealed within evacuated or gas-filled containers for the purpose of eliminating undesirable effects on their characteristics due to changes of atmospheric pressure, temperature and humidity. This general type of condenser is constructed either with a fixed capacitance value, or with means for varying the capacitance of the condenser. v

' It is an object of the invention to form an enclosed variable electrical condenser of such improved structural features as to enable adjustment externally, to impart shock resistance, and to enable the unit to withstand high electrical potentials.

Other objects and novel features will be apparent from a consideration of the specification and the accompanying drawing illustrating a specific embodiment, the single view being a 1ongitudinal cross-sectional view.

Hermetically sealed envelope Il) enclosing the plates of the illustrative condenser is formed with a metal end section I2, a cylindrical glass section I4, a metal section I6 and a glass end section I8 joined together with hermetic seals in the order named.

Stationary member of the illustrative condenser comprises plural cylindrical plates 20a. Adjustable member 22 is formed in this instance to include plural cylindrical plates 22al interposed With and in spaced relation to fixed plates 20a.

Stationary member 20 is secured to end metallic section I2 of the envelope, which serves as an external terminal for the condenser.

Adjustable member 22 is supported by means of a conductive shaft 24 rotatably mounted in bearings 32 and 34 in metal plug 30 within envelope section i6. Endwise movement of member 22 and variation of the capacity of the condenser is achieved by means of a threaded portion 28 of shaft 24 in a female thread 36 in plug 30. A permanent magnet 26 is secured to the shaft within glass section I8 of the envelope that is non-magnetic. A soft-iron armature is rotatably supported outside envelope portion I8, and here takesthe form of a O-shaped yoke 38 having axially extended faces 40a and 40h. These faces are approximately equal to the total range of axial adjustment of member 22, plus the axial extentxof magnet 26.

Direct, low-resistance contact to the adjustable memberI isjjhobtained by means of silver-plated wiper contacts 36a and 36h which engage conductive shaft 24 that is also advantageously silverplated. The Wiper contacts are attached to metallic section I6.' This connection is supplemented by the electrical path across bearing 32.

The only moving contacts and the closely spaced portions of the fixed and adjustable members are guarded by the envelope from deterioration because of mechanical deformation and injury by atmospheric action. Fixed connections to the mutually adjustable condenser parts can be made directly to metal envelope portions I2 and I6. These envelope sections are illustrated as mechanically supported by straps 42 and 44 on base 46 of insulating material. Yoke 38 is supported on base 46 by post 48 which also forms a rotary bearing for the yoke and inhibits endwise travel of the yoke.

Adjustment of the condenser from the extreme minimum to the maximum and reversely is achieved by rotating yoke 38 about envelope section I8. This causes bar magnet 26 to rotate and operate screw 28 axially. Rotation is effected manually by grasping knob 50 attached to yoke 38, or by any other suitable driving means. The capacity of the condenser is indicated by the position of magnetic bar 26 opposite markings 4I.

The arrangement of yoke 38 of large axial extent opposite a small bar magnet is effective and economical. However, various modifications of this arrangement will be apparent to those skilled in the art. Part 26 may be formed as a softiron armature and yoke 38 may include a permanent magnetic section or an electromagnet establishing a field between faces 40a and 40h, for broadly comparable advantage. Additionally, part 26 might be made of considerable axial extent and faces 40a and 40h could be of limited axial extent, This would further extend the axial dimension of the structure shown and for thatreason the illustrated arrangement is preferred. One face 40 could be arranged to serve the purpose of yoke 38 generally.

Breakdown potential is dependent upon the dielectric medium between the condenser plates and may be increased by appropriate fill within the envelope or by evacuation. The breakdown limit is also affected by the axial extent and surface characteristics of envelope section I4 which may be increased as required by surface coating, by external ribs and other known expedients. The mechanical stability afforded by bearings 32 and 34 which are spaced apart lends electrical achieving adjustment of an enclosed condenser the particular illustrative form isv naturallt7 capa` ble of a certain latitude of rearrangement and substitution of detail, as welll aswide application in varied electrical organizations. Therefore the appended claims should be allowed such broad interpretation as is commensurate vwith thefspirit and scope of the invention. A

What is claimed is: l 1. A variable electrical condenser comprising an envelopefhavin'g a transparent portion anda pair of metallic sections mutually separated and joined to an interposed glassasection, atleast two cylindrical plates enclosed within said envelope and electrically and mechanically connected respectively to said metal envelope sections, one ofv said platesfbeing axially movable intelescopic relation to another of` said'l plates, said4 movable plate being supported on-an axially movable shaft and having secured thereto a magnetic element also enclosed within said'- transparent portion of said envelope, rotatable external magnetic means co-acting with said enclosed magnetic element for shifting said shaft' axially and having an axial extent at least equal to the transverse of said enclosed magnetic elementi'said transparent envelope portion having scale mar-kings opposite said enclosed magnetic element.

2. A variable electrical condenser comprising an evacuated envelope, apair of plates enclosed `within said envelope, adjustable supporting means secured to one of said plates comprising a shaft having a threaded portion, a threaded element xed in relation to said envelope and receiving said threaded portion, a magnetic element extending transverse to said shaft and secured thereto, said magnetic element being enclosed within said envelope, and a further magnetic element rotatably supported external to said envelope in a bearing preventing its axial displacement relative to Ysaid envelope and having portions opposedfto andcooperating with said enclosed magnetic element, the axial extent of the portions of the external element being greater inaxial length'lthan the opposite portions of the n v enclosed magnetic element so as to cooperate with that enclosed element in all adjusted positions thereof.

. vHENRY C. M. LONGACRE?.

REFERENCES CITED yThe following references are of record in the le of this patent:

UNITED STATES VPATENTS Number Name i Date 1,557,725- Proctor Oct. 20, 1925v 1,625,330 Pinkus Apr. 19, 1927` 2,454,049 Floyd Nov. 16, 1948 2,464,716 Piton Mar. 15, 1949 2,511,338 Jennings June 13, 1950 FOREIGN APATENTS Y' Number Country Date 351,686 Germany Apr. 12, 1922 278,748 Great Britain Mar. 15, 1928 

